A variety of zwitterionic containing silanes and siloxane polymers are known and the use of some of them have been found to provide ionic cross-linking with the formation of siloxane gels and solid rubbers. The siloxane polymers which have heretofore been disclosed as forming gels by virtue of ionic cross-linking, however, require the use of particular reagents because of the difficulty and cost of making polymers which would enable sufficient cross-linking to achieve gels and solid rubbers.
For example, a type of elastomeric silicone zwitterionomers are disclosed in U.S. Pat. No. 4,525,567, issued Jun. 25, 1985, to Campbell et al. The zwitterionomers disclosed which exhibit ionic cross-linking and form gels or solid rubber are characterized as being sultone based zwitterionomers whereas in contrast thereto the composition of the present invention are sulfur free, amic-acid or pyrrolidone carboxy based zwitterionomers. A further distinction exists between the Campbell et al products and the instant invention wherein the reactions may be conducted in the presence of silicone oils or other preferred solvents.
In U.S. Pat. No. 3,956,353, issued May 11, 1976 to Plueddemann, there is disclosed the reaction product of an aminofunctional silane and a cyclic acid anhydride. These reactants are limited, however, to vinyl benzyl functional amines which differ from the amine functional groups of the reactants of the present invention nor is there required such a substitution. Moreover, the products disclosed in the patent are low molecular weight monomers which are aqueous or alcohol coupling agent compositions, in contrast to the thickening compositions disclosed in the present invention.
In U.S. Pat. No. 5,008,424, Halloran et al., disclose zwitterionic aminofunctional siloxanes based on the reaction product of an aminofunctional siloxane and a cyclic acid anhydride for use in polish formulations. However, Halloran et al. discloses only low to medium molecular weight fluids and furthermore does not make mention of high molecular weight Zwitterionic fluids or the solvent thickening properties thereof.
U.S. Pat. No. 5,654,362, Schulz et al. disclose silicone oils and solvents thickened by utilizing cross-linked silicone elastomers, particularly the reaction of silicone hydride containing fluid with alpha, omega-diene catalyzed by platinum in the presence of a low molecular weight silicone oil. The present invention differs in that a zwitterionically cross-linked system is formed by inter and/or intra molecular non-covalent junctions. Schulz et al. further requires the gel to be mechanically forced under shear into a paste or powder when additional low molecular weight oil is added. Unlike Schulz et al., in the present invention, gel consistency is related in part to temperature and additional silicone oils or solvents may be added with heating when further dilution is required.
As such, the present invention provides new and unique advantages over typical prior art for thickened silicone oil formulations which will become apparent hereinafter.